并五苯薄膜晶体管及其应用

有机薄膜晶体管(TFT)在数据存储、集成电路、传感器诸方面的广泛应用引起了人们极大的兴趣.在有机TFT的研究中,并五苯TFT占有很重要的地位.介绍了并五苯薄膜晶体管的结构、工作原理及其应用,评述了该领域的研究进展,并对其前景进行了展望.     

Synergistic Effect of Excited State Property and Aggregation Characteristic of Organic Semiconductor on Efficient Hole-Transportation in Perovskite Device

Intrinsic characteristics of organic semiconductor-based hole transport materials (HTMs) such as facile synthesizability, energy level tunability, and charge transport capability have been highlighted as crucial factors determining the performances of perovskite photovoltaic (PV) cells. However, their properties in the excited state have not been actively studied, although PVs are operated under solar illumination. Here, the characteristics of organic HTMs in their excited state such as transition dipole moment can be a decisive factor that can improve built-in potential of PVs, consequently enhancing their charge extraction property as well as reducing carrier recombination. Moreover, the aggregation property of organic semiconductors, which has been an essential factor for high-performance organic HTMs to improve their carrier transport property, can induce a synergistic effect with their excited state property for the high-efficiency perovskite PVs. Additionally, it is also confirmed that their optical bandgaps, manipulated to have their absorption in the UV region, are beneficial to block UV light that degrades the quality of perovskite, consequently improving the stability of perovskite PV in p–i–n configuration. As a proof-of-concept, a model system, composed of triarylamine and imidazole-based organic HTMs, is designed, and it is believed that this strategy paves a way toward high-performance and stable perovskite PV devices.     

Metal-atom Interactions and Clustering in Organic Semiconductor Systems

The interatomic interactions and clustering of metal atoms have been studied by first-principles calculations in graphene, pentacene, and polyacetylene as representative organic systems. It is shown that long-range repulsive Coulomb interaction appears between metal atoms with small electronegativity such as Al due to their ionization on host organic molecules, inducing their scattered distribution in organic systems. On the other hand, metal atoms with large electronegativity such as Au are weakly bonded to organic molecules, easily diffuse in molecular solids, and prefer to combine with each other owing to their short-range strong metallic-bonding interaction, promoting metal cluster generation in organic systems.     

Analysis of Complete Organic Semiconductor Devices by Laser Desorption/Ionization Time‐of‐Flight Mass Spectrometry

In this contribution, it is shown that the method of laser‐desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOF‐MS) is a powerful technique for analyzing complete organic devices, such as organic light‐emitting diodes (OLEDs) or organic solar cells. LDI‐TOF‐MS has the potential to analyze fully processed organic devices without special pretreatment such as dissolving the device, peeling off the metal cathode, or using additional matrix materials. Thus, devices may be analysed as they are with a minimum of measurement artefacts. It is demonstrated that the method allows an analysis of complex organic multilayer devices, their composition, and incorporated impurities. It even allows possible electrochemical reaction products caused by device degradation to be analyzed. Thus, LDI‐TOF‐MS has major advantages compared to measurements of dissolved samples. As an example, the identification of all of the materials used in a complete OLED is shown. Furthermore, a detailed chemical analysis of long‐term driven OLEDs, including the detection of degradation products, is presented. From these data, several degradation mechanisms can be distinguished.     

Determining the Dielectric Constants of Organic Photovoltaic Materials Using Impedance Spectroscopy

The photovoltaic and electrical properties of organic semiconductors are characterized by their low dielectric constant, which leads to the formation of polarons and Frenkel excitons. The low dielectric constant of organic semiconductors has been suggested to be significantly influential in geminate and bimolecular recombination losses in organic photovoltaics (OPVs). However, despite the critical attention that the dielectric constant has received in literature discussions, there has not yet been a thorough study of the dielectric constant in common organic semiconductors and how it changes when blended. In fact, there have been some inconsistent and contradictory reports on such dielectric constants, making it difficult to identify trends. Herein, at first a detailed explanation of a specific methodology to determine the dielectric constant in OPV materials with impedance spectroscopy is provided, including guidelines for possible experimental pitfalls. Using this methodology, the analysis for the dielectric constant of 17 common neat organic semiconductors is carried out. Furthermore, the relationship between the dielectric constant and blend morphology are studied and determined. It is found that the dielectric constant of a blend system can be very accurately predicted solely based on the dielectric constants of the neat materials, scaled by their respective weight ratios in the blend film.     

Bandwidth and transient analysis of bilayer organic photodetectors

Utilization of organic photodetectors (OPDs) and their applications for assembling on flexible and curved substrates have increased in recent years. However, organic semiconductors suffer from low carrier mobility that demands an optimized design and precise modeling for their applications. The OPDs frequency bandwidth is one of the most important criteria that needs to be investigated carefully. In this paper a comprehensive physical time-domain framework is introduced for bandwidth calculations as well as other several evaluation criteria. This model is verified by experimental measurements. According to the results, increasing the reverse bias voltage boosts the bandwidth of OPD owing to the increase of the carrier mobility. Based on the introduced simulation approach, the trade-off between the bandwidth and the responsivity has been investigated and an efficient design method is also proposed which could effectively improve the OPD performance.     

Molecular Stacking Induced by Intermolecular C–H···N Hydrogen Bonds Leading to High Carrier Mobility in Vacuum‐Deposited Organic Films

Simple bottom‐up fabrication processes for molecular self‐assembly have been developed for the construction of higher‐order structures using organic materials, and have contributed to maximization of the potential of organic materials in chemical and bioengineering. However, their application to organic thin‐film devices such as organic light‐emitting diodes have not been widely considered because simple fabrication of a solid film containing an internal self‐assembly structure has been regarded as difficult. Here it is shown that the intermolecular C–H···N hydrogen bonds can be simply formed even in vacuum‐deposited organic films having flat interfaces. By designing the molecules containing pyridine rings properly for the intermolecular interaction, one can control the molecular stacking induced by the intermolecular hydrogen bonds. It is also demonstrated that the molecular stacking contributes to the high carrier mobility of the film. These findings provide new guidelines to improve the performance of organic optoelectronic devices and open up the possibilities for further development of organic devices with higher‐order structures.     

Analytical modeling of organic solar cells including monomolecular recombination and carrier generation calculated by optical transfer matrix method

An analytical model of organic solar cell has been developed including the effect of monomolecular recombination and charge carrier generation rate, simultaneously. The charge carrier generation rate, depending on position and wavelength, obtained from optical transfer matrix method, has been incorporated into electrical transport equation of carriers; this has led to combining optical and electrical phenomena into this model. Charge carrier generation rate profile has been investigated and included to develop the model. The proposed model addresses the propagation of light and the effects of optical phenomena like reflection and interference inside the device. Compared to previous models, this model is an improved version because of considering recombination mechanism and position and wavelength dependent generation rate simultaneously. This analytical model is useful for finding the performance of the organic solar cell device such as current-voltage relation, power-voltage relation, efficiency, etc. avoiding the complexities of numerical calculations. The proposed model has been validated by comparing the results obtained from the model with that of published experimental works. This model may help to analyse organic solar cells and optimize their parameters for improving the performance.     

A DC and small signal AC model for organic thin film transistors including contact effects and non quasi static regime

We present a compact model for the DC and small signal AC analysis of Organic Thin Film Transistors (OTFTs). The DC part of the model assumes that the electrical current injected in the OTFT is limited by the presence of a metal/organic semiconductor junction that, at source, acts as a reverse biased Schottky junction. By including this junction, modeled as a reverse biased gated diode at source, the DC model is able to reproduce the scaling of the electrical characteristics even for short channel devices.The small signal AC part of the model uses a transmission line approach in order to compute the impedances of the channel and parasitic regions of the device. The overlap capacitances and the presence of non-ideal metal/organic semiconductor junctions are taken in account as well and the model can be easily adapted to different device geometries. The model is particularly well suited for printed devices, often realized with large process tolerances, since it takes into consideration the presence of parasitic regions and their effect on the AC operation.The model has been validated on printed OTFTs using a pentace-derivative as organic semiconductor with a quite peculiar device layout. It has been fully implemented in Verilog-A programming language.     

水溶性有机去膜液的主要成分及其作用原理概述

文章在大量的文献基础上总结了水溶性有机去膜液的主要成分,包括有机胺、有机溶剂、加速剂、缓蚀剂和消泡剂,并介绍了各种成分在去膜过程中的作用原理。重点介绍应用于去膜液中的各类缓蚀剂及其缓蚀机理,缓蚀剂包括含氮化合物、含硫化合物、有机酸、芳香族羟基化合物等。     

Selective Nucleation of Organic Single Crystals from Vapor Phase on Nanoscopically Rough Surfaces

Organic field‐effect transistors (OFETs) are attractive for microelectronic applications such as sensor arrays or flexible displays, due to their adequate performance and relatively low production costs. Organic single‐crystal transistors have emerged as benchmark devices for studying the intrinsic charge‐transport properties in organic semiconductor materials. Conventional approaches for growing organic single crystals result in uncontrollable dimensions and the formation of extremely fragile crystals. In addition, the hand‐selection and placement of individual crystals on a device structure represents a severe limitation for producing arrays of single‐crystal transistors with high density and reasonable throughput. As a result, the application of organic single‐crystal transistors has been restricted to fundamental charge transport studies, with their commercial application not yet realizable. We recently reported a materials‐general method of fabricating large‐area arrays of patterned organic single crystals. Microcontact‐printed octadecyltriethoxysilane (OTS) film domains on smooth, inert substrates were found to act as preferential nucleation sites for single crystals for a broad range of organic semiconductor materials, such as pentacene, tetracene, rubrene and C₆₀. In order to understand the underlying mechanism of preferential nucleation, the stamped OTS domains and the contact plane between the OTS domains and the organic crystals were inspected by atomic force microscopy (AFM) and optical microscopy. Our analysis suggests that crystals nucleate at the base of tall OTS pillars that form the significantly rough surface in the stamped domains. The selective nucleation inside the rough surface regions is discussed by means of a rate‐equation model of the growth process.     

Current Enhancement in Organic Films through Gap Compression by Cold and Hot Isostatic Pressing

The spatial gaps in organic films are compressed using cold and hot isostatic pressing (CIP and HIP, respectively) with the aim of enhancing their electrical characteristics. The microscopic gaps formed in amorphous organic films by inefficient molecular packing are difficult to compress using CIP and HIP; however, the macroscopic gaps formed between grains and other grains or substrates in polycrystalline organic films can be compressed using CIP and HIP. The gap compression by CIP and HIP in polycrystalline films enhances their electrical characteristics. Conversely, the electrical characteristics of amorphous films remain unchanged after CIP and HIP. HIP gives almost the same results as CIP in terms of gap compression and current enhancement, probably because the expected activation of molecular motion at high temperature is suppressed under high applied pressure. CIP markedly improves the performance of organic light‐emitting diodes, organic solar cells, and organic field‐effect transistors containing polycrystalline films. These findings are important for understanding the carrier injection and transport mechanisms of organic films containing gaps as well as enhancing the performance of future organic devices, especially those with polycrystalline films.     

浅析有机电致发光器件电输运特性的数值模拟

有机电致发光器件因为其独特的优点,得到了广泛的重视,本文用数值模拟的方法研究有机电致发光器件的载流子输运性质,分别研究单层结构的有机电致发光器件,肖特基接触下的电流注入的特性,在以上基础上研究多层复杂结构的有机电致发光器件的载流子的注入传输等性质,并研究其发光特性。最后在加入热力学方程,研究其热学性质。     

Generation-recombination in disordered organic semiconductor: Application to the characterization of traps

The presence of traps in organic semiconductor based electronic devices affects considerably their performances and their stability. The Shockley-Read-Hall (SRH) model is generally used to extract the trap parameters from the experimental results. In this paper, we propose to adapt the SRH formalism to disordered organic semiconductors by considering a hopping transport process and Gaussian distributions for both mobile and trapped carriers. The model is used to extract multiple trap parameters from charge based Deep Level Transient Spectroscopy (Q-DLTS) spectrum. Calculation of the charge transients are given in detail. The model predicts that the activation energy of the trap should not follow an Arrhenius plot on large temperature ranges. Also, the charge transients are no longer exponential when considering Gaussian trap distributions, enlarging the Q-DLTS peaks. The model fits the Q-DLTS spectra measured on organic diodes with a limited number of trap contributions with a good agreement. It is found that an increase of the material rate of disorder reduces the extracted trap energy distances to the LUMO but has no influence on the extracted trap distribution widths. This work shows the importance of considering the specific properties of organic materials to study their properties and their trap distributions.     

有机发光器件(OLED)封装技术的研究现状分析

有机发光器件(OLED)诞生至今,封装方式一直是提高其寿命和稳定性的重要因素之一,也是当前研究的热点。从最初的后盖式封装发展到现在的薄膜封装,其寿命和稳定性也随之提高,人们幻想的柔性显示也成为了现实。新的有效封装方法的出现使有机发光器件从实验室走进了人们的日常生活,并有望成为下一代显示器的主流。文章重点介绍了当今主要的封装技术和方法,提出了结合传统后盖式封装和薄膜封装的混合封装方法。     

Controllable molecular doping in organic single crystals toward high-efficiency light-emitting devices

Organic single-crystalline semiconductors have drawn significant attention in the area of organic electronic and optoelectronic devices due to their superiorities of highly ordered structure, high carrier mobility and low impurity content. Molecular doping technique has made great progress in improving device performance via optimizing the optical and electrical properties of organic semiconductors. In particular, this technique has been attempted by taking fluorescent dye-molecules as the emissive dopants to tune emission color and improve device performance of organic single crystals. Up to now, there are few reports about the use of molecular doping in organic single crystals to optimize their intrinsic electrical properties. Here, we have introduced the controllable molecular doping as a feasible approach toward manipulating charge carrier transport properties of organic single crystals. Upon optimization of doping concentration, balanced carrier transport can be realized in 5,5′-bis(4-trifluoromethyl phenyl) [2,2’] bithiophene (P2TCF₃)-doped 1,4-bis(4-methylstyryl) benzene (BSB–Me) crystals. Organic light-emitting devices (OLEDs) based on these doped crystals achieve a maximum luminance of 423 cd/m² and current efficiency of 0.48 cd/A. It demonstrates that high-efficiency crystal-based OLEDs are of great significance for the development of organic electronics, especially for display and lighting applications.     

Organic Synaptic Transistors: The Evolutionary Path from Memory Cells to the Application of Artificial Neural Networks

The progress of neural synaptic devices is experiencing an era of explosive growth. Given that the traditional storage system has yet to overcome the von Neumann bottleneck, it is critical to develop hardware with bioinspired information processing functions and lower power consumption. Transistors based on 2D materials, metal oxides, and organic materials have been adopted to mimic the synapse of a human brain, due to their high plasticity, parallel computing, integrated storage, and system information processing. Among these materials used to build transistors, organic semiconductors are considered to be the most promising candidate for neural synaptic devices and bio-electronics, owing to their easy processing, mechanical flexibility, low cost, good bio-compatibility, and ductility. This review focuses on the recent advances in organic synaptic devices with various structures, materials, and working mechanisms. The applications of artificial neural networks that integrate multiple organic synaptic transistors are also concretely discussed. Finally, the challenges that organic synaptic devices currently face are discussed and future developments are forecast.     

Realizing the Potential of ZnO with Alternative Non‐Metallic Co‐Dopants as Electrode Materials for Small Molecule Optoelectronic Devices

High performance indium tin oxide (ITO)‐free small molecule organic solar cells and organic light‐emitting diodes (OLEDs) are demonstrated using optimized ZnO electrodes with alternative non‐metallic co‐dopants. The co‐doping of hydrogen and fluorine reduces the metal content of ZnO thin films, resulting in a low absorption coefficient, a high transmittance, and a low refractive index as well as the high conductivity, which are needed for the application in organic solar cells and OLEDs. While the established metal‐doped ZnO films have good electrical and optical properties, their application in organic devices is not as efficient as other alternative electrode approaches. The optimized ZnO electrodes presented here are employed in organic solar cells as well as OLEDs and allow not only the replacement of ITO, but also significantly improve the efficiency compared to lab‐standard ITO. The enhanced performance is attributed to outstanding optical properties and spontaneously nanostructured surfaces of the ZnO films with non‐metallic co‐dopants and their straightforward integration with molecular doping technology, which avoids several common drawbacks of ZnO electrodes. The observations show that optimized ZnO films with non‐metallic co‐dopants are a promising and competitive electrode for low‐cost and high performance organic solar cells and OLEDs.     

Interface electronic structure between organic semiconductor film and electrode metal probed by photoelectron yield spectroscopy

We present an investigation of the interface between organic semiconductor films and metal substrates (organic/metal interface) using photoelectron yield spectroscopy (PYS) as the probing technique. PYS studies were conducted on the pentacene/Au, copper phthalocyanine (CuPc)/Au, and perfluorinated zinc phthalocyanine (F₁₆ZnPc)/Au, and the results were compared with literature results obtained using conventional ultraviolet photoemission spectroscopy (UPS). PYS is advantageous for probing the electronic structure of the organic/metal interface because of the relatively long mean free path of photoexcited electrons with very low kinetic energy in PYS, which enables the detection of the photoelectrons from the metal substrate buried deep in the organic film. We demonstrate herein that the use of PYS reduces the significance of the final state effect of the electronic density surrounding the photohole at the organic molecule generated after the photoemission; this effect is known as the electric polarization effect. Although this effect has a significant influence on the results obtained using conventional UPS, the reduced influence of the final state effect in PYS makes it possible to construct an energy level diagram at the organic/metal interface with greater accuracy than can be achieved with UPS. In addition, a novel mechanism of the photoelectron detection for PYS enables us to apply PYS to very thick organic films, and therefore, PYS provides a reliable value of ionization energy for organic films without the influence of the substrate.Because the interface electronic structure has a significant influence on the carrier injection properties of organic devices, the increased reliability of the information obtained by PYS will render it very useful for the improvement of device performance as well for understanding their operation principles.     

Two-dimensional crystal growth of thermally converted organic semiconductors at the surface of ionic liquid and high-mobility organic field-effect transistors

We report a novel solution-crystallization method to grow two-dimensional platelet-shaped single-crystals of well-known insoluble organic semiconductors via thermal conversion of their precursor molecules dissolved in ionic liquids (ILs). By optimizing conditions of the crystal growth regarding physical properties of ILs such as density and viscosity, we successfully and reproducibly obtained thin platelets of pentacene and dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) single-crystals, with which nearly the best performing field-effect transistors are constructed for the two compounds. The prompt and simple technique has opened the way to use practically insoluble organic semiconductor materials for high-performance printed electronics, which enables mass-producible and large-area organic circuitry devices.